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- Creators: Debussy, Claude, 1862-1918
Description
Growth of the Phoenix metropolitan area led to exposures of the internal bedrock structure of surrounding semi-arid mountain ranges as housing platforms or road cuts. Such exposures in the Sonoran and Mojave deserts reveal the presence of sedimentary calcium carbonate infilling the pre-existing fracture matrix of the bedrock. Field surveys of bedrock fractures filled with carbonate (BFFC) reveal an average of 0.079 +/- 0.024 mT C/m2 stored in the upper 2 m of analyzed bedrock exposures. Back-scattered electron microscopy images indicate the presence of carbonate at the micron scale, not included in this estimation. Analysis of the spatial extent of bedrock landforms in arid and semi-arid regions worldwide suggests that ~1485 GtC could potentially be stored in the upper 2 m horizon of BFFCs. Radiocarbon dating obtained at one of the sites indicates it is likely that some of the carbonate was flushed into the bedrock system during glacial wet pulses, and is stored on Pleistocene timescales or longer. Strontium isotope analysis at the same site suggest the potential for a substantial cation contribution from weathering of the local bedrock, indicating the potential exists for sequestration of atmospheric carbon in BFFCs. Rates of carbon release from BFFCs are tied to rates of erosion of bedrock ranges in desert climates.
ContributorsHarrison, Emma (Author) / Dorn, Ronald (Thesis advisor) / Reynolds, Stephen (Committee member) / Schmeeckle, Mark (Committee member) / Arizona State University (Publisher)
Created2013
Description
A fundamental gap in geomorphic scholarship regards fluvial terraces in small desert drainages and those terraces associated with integrating drainages. This dissertation analyzes four field-based case studies within the Sonoran Desert, south-central Arizona, with the overriding purpose of developing a theory to explain the formative processes and spatial distribution of fluvial terraces in the region. Strath terraces are a common form (Chapters 2, 3, 4) and are created at the expense of bounding pediments that occur on the margins of constraining mountainous drainage boundaries (Chapters 1, 2, 3). Base-level fluctuations of the major drainages cause the formation of new straths at lower elevations. Dramatic pediment adjustment and subsequent regrading follows (Chapter 3), where pediments regrade to strath floodplains. This linkage between pediments and their distal straths is termed the pediment-strath relationship. Stability of the base level of the major drainage leads to lateral migration and straths are carved at the expense of bounding pediments through an erosional asymmetry facilitated by differential rock decay between the channel bank and bed. Fill terraces occur within the Salt River drainage basin as a result of the integration processes that connect formerly endorheic basins (Chapter 4). The topographic, spatial, and sedimentologic relationship of the Stewart Mountain terrace (Chapter 4) points to a different genetic origin than the lower terraces in this basin. The high Stewart Mountain fill terrace records the initial integration of this river. The strath terraces inset below the Stewart Mountain terrace are a result of the pediment-strath relationship. These case studies also reveal that the under-addressed drainage processes of piracy and overflow have significant impacts in the evolution of drainages the lead to both strath and fill terrace formation in this region.
ContributorsLarson, Phillip Herman (Author) / Dorn, Ron I (Thesis advisor) / Schmeeckle, Mark (Thesis advisor) / Douglass, John (Committee member) / Cerveny, Randy (Committee member) / Arizona State University (Publisher)
Created2013
Description
Ephemeral streams in Arizona that are perpendicularly intersected by the Central Arizona Project (CAP) canal have been altered due to partial or complete damming of the stream channel. The dammed upstream channels have experienced decades long cycles of sediment deposition and waterlogging during storm events causing the development of "green-up" zones. This dissertation examines the biogeomorphological effects of damming ephemeral streams caused by the CAP canal by investigating: (1) changes in the preexisting spatial cover of riparian vegetation and how these changes are affected by stream geometry; (2) green-up initiation and evolution; and (3) changes in plant species and community level changes. To the author's knowledge, this is the only study that undertakes an interdisciplinary approach to understanding the environmental responses to anthropogenically-altered ephemeral stream channels. The results presented herein show that vegetation along the upstream section increased by an average of 200,872 m2 per kilometer of the CAP canal over a 28 year period. Vegetation growth was compared to channel widths which share a quasi-linear relationship. Remote sensing analysis of Landsat TM images using an object-oriented approach shows that riparian vegetation cover gradually increased over 28 years. Field studies reveal that the increases in vegetation are attributed to the artificial rise in local base-level upstream created by the canal, which causes water to spill laterally onto the desert floor. Vegetation within the green-up zone varies considerably in comparison to pre-canal construction. Changes are most notable in vegetation community shifts and abundance. The wettest section of the green-up zone contains the greatest density of woody plant stems, the greatest vegetation volume, and a high percentage of herbaceous cover. Vegetation within wetter zones changed from a tree-shrub to a predominantly tree-herb assemblage, whereas desert shrubs located in zones with intermediate moisture have developed larger stems. Results from this study lend valuable insight to green-up processes associated with damming ephemeral streams, which can be applied to planning future canal or dam projects in drylands. Also, understanding the development of the green-up zones provide awareness to potentially avoiding flood damage to infrastructure that may be unknowingly constructed within the slow-growing green-up zone.
ContributorsHamdan, Abeer (Author) / Schmeeckle, Mark (Thesis advisor) / Myint, Soe (Thesis advisor) / Dorn, Ronald (Committee member) / Stromberg, Juliet (Committee member) / Arizona State University (Publisher)
Created2014
ContributorsDebussy, Claude, 1862-1918 (Composer)
ContributorsDebussy, Claude, 1862-1918 (Composer)
ContributorsDebussy, Claude, 1862-1918 (Composer)
ContributorsDebussy, Claude, 1862-1918 (Composer)
ContributorsDebussy, Claude, 1862-1918 (Composer)
Description
Human endeavors move 7x more volume of earth than the world’s rivers accelerating the removal of Earth’s soil surface. Measuring anthropogenic acceleration of soil erosion requires knowledge of natural rates through the study of 10Be, but same-watershed comparisons between anthropogenically-accelerated and natural erosion rates do not exist for urbanizing watersheds. Here I show that urban sprawl from 1989 to 2013 accelerated soil erosion between 1.3x and 15x above natural rates for different urbanizing watersheds in the metropolitan Phoenix region, Sonoran Desert, USA, and that statistical modeling a century of urban sprawl indicates an acceleration of only 2.7x for the Phoenix region. Based on studies of urbanization’s erosive effects, and studies comparing other land-use changes to natural erosion rates, we expected a greater degree of urban acceleration. Given that continued urban expansion will add a new city of a million every five days until 2050, given the potential importance of urban soils for absorbing anthropogenically-released carbon, and given the role of urban-sourced pollution, quantifying urbanization’s acceleration of natural erosion in other urban settings could reveal important regional patterns. For example, a comparison of urban watersheds to nearby non-urban watersheds suggests that the Phoenix case study is on the low-end of the urban acceleration factor. This new insight into the urban acceleration of soil erosion in metropolitan Phoenix can help reduce the acute risk of flooding for many rapidly urbanizing desert cities around the globe. To reduce this risk, properly engineered Flood Control Structures must account for sediment accumulation as well as flood waters. While the Phoenix area used regional data from non-urban, non-desert watersheds to generate sediment yield rates, this research presents a new analysis of empirical data for the Phoenix metropolitan region, where two regression models provide estimates of a more realistic sediment accumulation for arid regions and also urbanization of a desert cities. The new model can be used to predict the realistic sediment accumulation for helping provide data where few data exists in parts of arid Africa, southwest Asia, and India.
ContributorsJeong, Ara (Author) / Dorn, Ronald I. (Thesis advisor) / Schmeeckle, Mark (Committee member) / Walker, Ian J. (Committee member) / Arizona State University (Publisher)
Created2019
Description
ABSTRACT
The Sentinel-Arlington Volcanic Field (SAVF) is the Sentinel Plains lava field and associated volcanic edifices of late Cenozoic alkali olivine basaltic lava flows and minor tephra deposits near the Gila Bend and Painted Rock Mountains, 65 km-100km southwest of Phoenix, Arizona. The SAVF covers ~600 km2 and consists of 21+ volcanic centers, primarily low shield volcanoes ranging from 4-6 km in diameter and 30-200 m in height. The SAVF represents plains-style volcanism, an emplacement style and effusion rate intermediate between flood volcanism and large shield-building volcanism. Because of these characteristics, SAVF is a good analogue to small-volume effusive volcanic centers on Mars, such as those seen the southern flank of Pavonis Mons and in the Tempe Terra region of Mars. The eruptive history of the volcanic field is established through detailed geologic map supplemented by geochemical, paleomagnetic, and geochronological analysis.
Paleomagnetic analyses were completed on 473 oriented core samples from 58 sites. Mean inclination and declination directions were calculated from 8-12 samples at each site. Fifty sites revealed well-grouped natural remanent magnetization vectors after applying alternating field demagnetization. Thirty-nine sites had reversed polarity, eleven had normal polarity. Fifteen unique paleosecular variation inclination and declination directions were identified, six were represented by more than one site with resultant vectors that correlated within a 95% confidence interval. Four reversed sites were radiometrically dated to the Matuyama Chron with ages ranging from 1.08 ± 0.15 Ma to 2.37 ± 0.02 Ma; and one normal polarity site was dated to the Olduvai normal excursion at 1.91 ± 0.59 Ma. Paleomagnetic correlations within a 95% confidence interval were used to extrapolate radiogenic dates. Results reveal 3-5 eruptive stages over ~1.5 Ma in the early Pleistocene and that the SAVF dammed and possibly diverted the lower Gila River multiple times. Preliminary modeling of the median clast size of the terrace deposits suggests a maximum discharge of ~11300 cms (~400,000 cfs) was necessary to transport observed sediment load, which is larger than the historically recorded discharge of the modern Gila River.
The Sentinel-Arlington Volcanic Field (SAVF) is the Sentinel Plains lava field and associated volcanic edifices of late Cenozoic alkali olivine basaltic lava flows and minor tephra deposits near the Gila Bend and Painted Rock Mountains, 65 km-100km southwest of Phoenix, Arizona. The SAVF covers ~600 km2 and consists of 21+ volcanic centers, primarily low shield volcanoes ranging from 4-6 km in diameter and 30-200 m in height. The SAVF represents plains-style volcanism, an emplacement style and effusion rate intermediate between flood volcanism and large shield-building volcanism. Because of these characteristics, SAVF is a good analogue to small-volume effusive volcanic centers on Mars, such as those seen the southern flank of Pavonis Mons and in the Tempe Terra region of Mars. The eruptive history of the volcanic field is established through detailed geologic map supplemented by geochemical, paleomagnetic, and geochronological analysis.
Paleomagnetic analyses were completed on 473 oriented core samples from 58 sites. Mean inclination and declination directions were calculated from 8-12 samples at each site. Fifty sites revealed well-grouped natural remanent magnetization vectors after applying alternating field demagnetization. Thirty-nine sites had reversed polarity, eleven had normal polarity. Fifteen unique paleosecular variation inclination and declination directions were identified, six were represented by more than one site with resultant vectors that correlated within a 95% confidence interval. Four reversed sites were radiometrically dated to the Matuyama Chron with ages ranging from 1.08 ± 0.15 Ma to 2.37 ± 0.02 Ma; and one normal polarity site was dated to the Olduvai normal excursion at 1.91 ± 0.59 Ma. Paleomagnetic correlations within a 95% confidence interval were used to extrapolate radiogenic dates. Results reveal 3-5 eruptive stages over ~1.5 Ma in the early Pleistocene and that the SAVF dammed and possibly diverted the lower Gila River multiple times. Preliminary modeling of the median clast size of the terrace deposits suggests a maximum discharge of ~11300 cms (~400,000 cfs) was necessary to transport observed sediment load, which is larger than the historically recorded discharge of the modern Gila River.
ContributorsCave, Shelby Renee (Author) / Clarke, Amanda (Thesis advisor) / Burt, Donald (Committee member) / Reynolds, Stephen (Committee member) / Semken, Steven (Committee member) / Schmeeckle, Mark (Committee member) / Arizona State University (Publisher)
Created2015